Polycrystalline superabrasive materials like PCD and PCBN have been widely used for years in both metalworking and woodworking industries by virtue of their unique mechanical and physical properties. These superabrasive materials tend to have a high abrasive resistance, high toughness, and high hardness. However, these superabrasive materials have not been effective in other cutting tool industry especially in milling and drilling applications due primarily to availability and cost factors.
The main drawback is related to the unique design or shape of tool products in which the cutting face of PCD or PCBN is fluted or helical shaped for an effective cutting performance. Unfortunately, helical shapes are not readily fabricated from PCD or PCBN under HPHT sintering process due to complexity in cell designs in combination with their superhard material characteristics. Furthermore, any conventional shaping process in an attempt to put the flute or helical shape into a superabrasive material by finishing operations such as grinding is a very tedious and costly process. This is true even with superabrasive parts having a nearly net shape of a desirable final product design.
Historically, one main barrier preventing diamond or PCD tools from penetrating the market against conventional tool materials like either high speed steel or carbide has been the manufacturing cost. Currently, veined PCD drills made according to U.S. Pat. No. 5,580,196 of Abrasive Technology is an upgrade product over electroplated CVD coated or fabricated drills especially in aerospace and automotive industry. However, it has been reported that product life of these materials is short from failing fabrication joints and a lack of a rugged edge. In addition, the price of this tool is very expensive so that many potential consumers are reluctant to try.
U.S. Pat. No. 6,158,304 to Smith International, Inc. teaches a center cutting end mill having spiral grooves and flutes in the end mill substrate filled with polycrystalline diamond or cubic boron nitride formed or sintered in situ in the grooves to integrally bond via partial infiltration into the substrate. The PCD or PCBN materials as bonded in the grooves is then subsequently ground to a final shape by conventional techniques such as by grinding, wire electrical discharge cutting (EDM) or electrical discharge grinding (EDG). This process requires that the mill body and PCD or PCBN material both be subjected to high pressure, high temperature conditions and then the bonded PCD or PCBN be further reshaped to form a cutting edge.
Megadiamond has introduced carbide inserts with veins of PCD but which are only one inch long which requires a braze point to a carbide rod/shank of the same diameter. However, this is a mechanical weakness and makes flute grinding difficult, especially on automated grinders. Another weakness of these veined PCD end mill cutters is that they cannot resharpen an expensive tool because the PCD insert is too shallow. In short, although some progress has been made in the past few years, the rotary tool market within the cutting tool industry has long desired both the helical or fluted PCD drill tip and a reliable PCD fluted end mill that are cost competitive and reliable in tool performance over the existing superabrasive tools.